1. Field of the Invention
The present invention relates to a separator for fuel cell capable of improving the stack performance by reducing the deviation in cell performance and reducing the dead space, and a fuel cell stack using the same.
2. Description of the Related Art
In recent years, fuel cell separators have been used in fuel cell stacks having a plurality of stacked fuel cells. In this case, separators are disposed between two fuel cells functioning to supply fuel or oxidizing agent to adjacent fuel cells. The separators have also functioned to electrically couple two adjacent fuel cells to each other. Therefore, the separator generally includes a channel for supplying fuel to an anode of the fuel cell, and/or a channel for supplying oxidizing agent to a cathode of the fuel cell.
The fuel cell stack may be manufactured with various appearances and shapes corresponding to its intended applications. In particular, the fuel cell stack may be manufactured to have a structure in which a coupling hole is bored inside an active region of the fuel cell, or a structure in which a separator includes a cross channel region. Here, the stack structure in which a coupling hole is bored in the active region of the cell is to prevent a boundary region between the cell and the separator from being cracked when the separator is stacked on the cell. A stack structure in which a separator has a cross channel region may be used to obtain a maximum active region with the same stack volume.
A channel of the separator is generally coupled between an inlet manifold and an outlet manifold, which may be installed in a laminated fuel cell stack. When a plurality of channels are installed in one surface of one separator, the plurality of the channels extend from the inlet manifold to the outlet manifold with the inlet manifold aligned either parallel to the outlet manifold, or extending independently from each other.
However, in the case of the fuel cell stack in which a coupling hole is bored inside the active region of the cell, the presence of the coupling hole prevents the separator from having a plurality of channels extending parallel to each other. Also, when a plurality of channels extending independently of each other are installed in different regions in the fuel cell stack including a coupling hole inside the active region of the cell, the inlet manifold and the outlet manifold are disposed either in a central region of the top and bottom channel regions, or the left and right channel regions of the separator, both scenarios leading to increased dead space. Since the active region of the cell is reduced with the increase in the dead space, the power density per cell volume may be low.
Further, when a separator having a plurality of channels independently extended to different regions is used in the fuel cell stack, the inlet manifold and the outlet manifold are disposed in a diagonal direction with respect to the channel region of the separator. In this configuration a fuel flow rate concentration may be non-uniform in channel groups independently formed between the inlet manifold and the outlet manifold. Non-uniform fuel flow rate concentration may lead to deteriorated stack performance.